Composite magnetic sealing material

ABSTRACT

Disclosed herein is a composite magnetic sealing material includes a resin material and a filler blended in the resin material in a blended ratio of 30 vol. % or more to 85 vol. % or less. The filler includes a magnetic filler containing Fe and 32 wt. % or more and 39 wt. % or less of a metal material contained mainly of Ni, thereby a thermal expansion coefficient of the composite magnetic sealing material is 15 ppm/° C. or less.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a composite magnetic sealing materialand, more particularly, to a composite magnetic sealing materialsuitably used as a molding material for electronic circuit package.

Description of Related Art

In recent years, an electronic device such as a smartphone is equippedwith a high-performance radio communication circuit and ahigh-performance digital chip, and an operating frequency of asemiconductor IC used therein tends to increase. Further, adoption of anSIP (System-In Package) having a 2.5D or 3D structure, in which aplurality of semiconductor ICs are connected by a shortest wiring, isaccelerated, and modularization of a power supply system is expected toaccelerate. Further, an electronic circuit module having a large numberof modulated electronic components (collective term of components, suchas passive components (an inductor, a capacitor, a resistor, a filter,etc.), active components (a transistor, a diode, etc.), integratedcircuit components (an semiconductor IC, etc.) and other componentsrequired for electronic circuit configuration) is expected to becomemore and more popular, and an electronic circuit package which is acollective term for the above SIP, electronic circuit module, and thelike tends to be mounted in high density along with sophistication,miniaturization, and thinning of an electronic device such as asmartphone. However, this tendency poses a problem of malfunction andradio disturbance due to noise. The problem of malfunction and radiodisturbance is difficult to be solved by conventional noisecountermeasure techniques. Thus, recently, self-shielding of theelectronic circuit package has become accelerated, and anelectromagnetic shielding using a conductive paste or a plating orsputtering method has been proposed and put into practical use, andhigher shielding characteristics are required in the future.

To achieve this, recently, there are proposed electronic circuitpackages in which a molding material itself has magnetic shieldingcharacteristics. For example, Japanese Patent Application Laid-Open No.H10-64714 discloses a composite magnetic sealing material added withsoft magnetic powder having an oxide film as a molding material forelectronic circuit package.

However, conventional composite magnetic sealing materials have adrawback in that it has a large thermal expansion coefficient. Thus, amismatch occurs between a composite magnetic sealing material and apackage substrate or electronic components in terms of the thermalexpansion coefficient. As a result, an aggregated substrate having astrip shape after molding may be greatly warped, or there may occur awarp large enough to cause a problem with connectivity of an electroniccircuit package in a diced state in mounting reflow. This phenomenonwill be described in detail below.

In recent years, various structures have been proposed for and actuallyput into practical use as a semiconductor package or an electroniccomponent module, and, currently, there is generally adopted a structurein which electronic components such as semiconductor ICs are mounted onan organic multilayer substrate, followed by molding of the upperportion and periphery of the electronic component package by a resinsealing material. A semiconductor package or electronic component modulehaving such a structure is molded as an aggregated substrate, followedby dicing.

In this structure, an organic multilayer substrate and a resin sealingmaterial having different physical properties constitute a so-calledbimetal, so that a warp may occur due to the difference between thermalexpansion coefficients, glass transition, or curing shrinkage of amolding material. To suppress the warp, it is necessary to make thephysical properties such as thermal expansion coefficients coincide witheach other as much as possible. In recent years, an organic multilayersubstrate used for a semiconductor package or an electronic circuitmodule is getting thinner and thinner and is increasing in the number oflayers thereof to meet requirements for height reduction. In order torealize high rigidity and low thermal expansion for ensuring goodhandleability of a thin substrate while achieving the thicknessreduction and multilayer structure, use of a substrate material having ahigh glass transition temperature, addition of a filler having a smallthermal expansion coefficient to a substrate material, or use of glasscloth having a smaller thermal expansion coefficient is a commonpractice at present.

On the other hand, the difference in physical properties betweensemiconductor ICs and electronic components mounted on a substrate and amolding material also generates a stress, causing various problems suchas interfacial delamination of the molding material and crack of theelectronic components or molding material. Incidentally, silicon is usedas the semiconductor ICs. The thermal expansion coefficient of siliconis 3.5 ppm/° C., and that of a baked chip component such as a ceramiccapacitor or an inductor is about 10 ppm/° C.

Thus, the molding material is also required to have a small thermalexpansion coefficient, and some commercially-available materials have athermal expansion coefficient below 10 ppm/° C. As a method for reducingthe thermal expansion coefficient of the molding material, adopting anepoxy resin having a small thermal expansion coefficient, as well as,blending molten silica having a very small thermal expansion coefficientof 0.5 ppm/° C. in a sealing resin at a high filling rate can be taken.

General magnetic materials have a high thermal expansion coefficient.Thus, as described in Japanese Patent Application Laid-Open No.H10-64714, the composite magnetic sealing material obtained by addinggeneral soft magnetic powder to a mold resin cannot achieve a targetsmall thermal expansion coefficient.

SUMMARY

An object of the present invention is therefore to provide a compositemagnetic sealing material having a small thermal expansion coefficient.

A composite magnetic sealing material according to the present inventionincludes a resin material and a filler blended in the resin material ina blended ratio of 30 vol. % or more to 85 vol. % or less. The fillerincludes a magnetic filler containing Fe and 32 wt. % or more and 39 wt.% or less of a metal material contained mainly of Ni, thereby a thermalexpansion coefficient of the composite magnetic sealing material is 15ppm/° C. or less.

According to the present invention, the thermal expansion coefficient ofthe composite magnetic sealing material can be reduced to 15 ppm/° C. orless by using the magnetic filler having a small thermal expansioncoefficient. Thus, when the composite magnetic sealing materialaccording to the present invention is used as a molding material for anelectronic circuit package, it is possible to prevent the warp of thesubstrate, interfacial delamination or crack of a molding material.

In the present invention, the metal material may further contain 0.1 wt.% or more and 8 wt. % or less of Co relative to the total weight of themagnetic filler. This enables a further reduction in the thermalexpansion coefficient of the composite magnetic sealing material.

In the present invention, the filler may further include a non-magneticfiller. This enables a further reduction in the thermal expansioncoefficient of the composite magnetic sealing material. In this case,the ratio of the amount of the non-magnetic filler relative to the sumof the amounts of the magnetic filler and the non-magnetic filler ispreferably 1 vol. % or more and 40 vol. % or less. This enables afurther reduction in the thermal expansion coefficient of the compositemagnetic sealing material while ensuring sufficient magneticcharacteristics. In this case, the non-magnetic filler preferablycontains at least one material selected from the group consisting ofSiO₂, ZrW₂O₈, (ZrO)₂P₂O₇, KZr₂(PO₄)₃, or Zr₂ (WO₄) (PO₄)₂. Thesematerials have a very small or negative thermal expansion coefficient,thus enabling a further reduction in the thermal expansion coefficientof the composite magnetic sealing material.

In the present invention, the magnetic filler preferably has asubstantially spherical shape. This enables an increase in the ratio ofthe magnetic filler to the composite magnetic sealing material.

In the present invention, the surface of the magnetic filler ispreferably insulatively coated, and the film thickness of the insulatingcoating is preferably 10 nm or more. With this configuration, the volumeresistivity of the composite magnetic sealing material can be increasedto, e.g., 10¹⁰ Ωcm or more, making it possible to ensure insulatingperformance required for a molding material for an electronic circuitpackage.

In the present invention, the resin material is preferably athermosetting resin material, and the thermosetting resin materialpreferably contains at least one material selected from the groupconsisting of an epoxy resin, a phenol resin, a urethane resin, asilicone resin, or an imide resin.

As described above, the composite magnetic sealing material according tothe present invention has a small thermal expansion coefficient. Thus,when the composite magnetic sealing material is used as a sealingmaterial for an electronic circuit package, it is possible to preventthe warp of the substrate, interfacial delamination or crack of amolding material.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will be moreapparent from the following description of certain preferred embodimentstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view for explaining a configuration of a compositemagnetic sealing material according to a preferred embodiment of thepresent invention;

FIG. 2 is a graph illustrating the relationship between the Ni ratio ofthe magnetic filler and the thermal expansion coefficient and themagnetic permeability of the composite magnetic sealing material;

FIG. 3 is a graph illustrating the relationship between the Ni ratio ofthe magnetic filler and the thermal expansion coefficient of thecomposite magnetic sealing material;

FIG. 4 is a graph illustrating the relationship between the Ni ratio ofthe magnetic filler and the magnetic permeability of the compositemagnetic sealing material;

FIG. 5 is a graph illustrating the relationship between the Co ratio ofthe magnetic filler and the thermal expansion coefficient and magneticpermeability of the composite magnetic sealing material;

FIG. 6 is a graph illustrating the relationship between the additiveratio of the non-magnetic filler and the thermal expansion coefficientof the composite magnetic sealing material;

FIG. 7 is a graph illustrating the relationship between thepresence/absence of the insulating coat formed on the surface of themagnetic filler and volume resistivity;

FIG. 8 is a graph illustrating the relationship between the filmthickness of the insulating coat formed on the surface of the magneticfiller and volume resistivity;

FIG. 9 is a graph illustrating the relationship between the volumeresistivity of the magnetic filler 6 and that of the composite magneticsealing material 2.

FIGS. 10A and 10B are schematic cross-sectional views illustrating astructure of an electronic circuit package using the composite magneticsealing material;

FIG. 11 is a graph illustrating noise attenuation in the electroniccircuit package shown in FIG. 10B;

FIGS. 12 to 14 are graphs each illustrating the relationship between thefilm thickness of the metal film included in the electronic circuitpackage shown in FIG. 10B and noise attenuation;

FIGS. 15 and 16 are graphs illustrating the warp amount of the substrateduring temperature rising and that during temperature dropping in theelectronic circuit packages shown in FIGS. 10A and 10B;

FIG. 17 is a table indicating compositions 1 to 3; and

FIGS. 18 and 19 are tables indicating measurement results of theExamples.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will be explained belowin detail with reference to the accompanying drawings.

FIG. 1 is a schematic view for explaining a configuration of a compositemagnetic sealing material according to a preferred embodiment of thepresent invention.

As illustrated in FIG. 1, a composite magnetic sealing material 2according to the present embodiment includes a resin material 4, and amagnetic filler 6 and a non-magnetic filler 8 which are blended in theresin material 4. Although not especially limited, the resin material 4is preferably composed mainly of a thermosetting resin material.Specifically, the resin material 4 is preferably composed mainly of anepoxy resin, a phenol resin, a urethane resin, a silicone resin, or animide resin and more preferably uses a base resin and a curing agentused for an epoxy resin-based or a phenol resin-based semiconductorsealing material.

The most preferable is the epoxy resin having a reactive epoxy group atits terminal, which can be combined with various types of curing agentsand curing accelerators. Examples of the epoxy resin include a bisphenolA epoxy resin, a bisphenol F epoxy resin, a phenoxy type epoxy resin, anaphthalene type epoxy resin, a multifunctional-type epoxy resin(dicyclopentadiene type epoxy resin, etc.), a biphenyl-type(bifunctional) epoxy resin, and an epoxy resin having a specialstructure. Among them, the biphenyl type epoxy resin, naphthalene typeepoxy resin, and dicyclopentadiene type epoxy resin are useful sincethey can attain low thermal expansion. Examples of the curing agent orcuring accelerator include amine-based compound alicyclic diamine,aromatic diamine, other amine-based compounds (imidazole, tertiaryamine, etc.), an acid anhydride compound (high-temperature curing agent,etc.), a phenol resin (novolac type phenol resin, cresol novolac typephenol resin, etc.), an amino resin, dicyandiamide, and a Lewis acidcomplex compound. For material kneading, known means such as a kneader,three-roll mills, or a mixer may be used.

The magnetic filler 6 is formed of an Fe—Ni based material and contains32 wt. % or more and 39 wt. % or less of a metal material composedmainly of Ni. The remaining 61-68 wt. % is Fe. The blending ratio of themagnetic filler 6 to the composite magnetic sealing material 2 is 30vol. % or more and 85 vol. % or less. When the blending ratio of themagnetic filler 6 is less than 30 vol. %, it is difficult to obtainsufficient magnetic characteristics; on the other hand, when theblending ratio of the magnetic filler 6 exceeds 85 vol. %, it isdifficult to ensure characteristics, such as flowability, required for asealing material.

The metal material composed mainly of Ni may contain a small amount ofCo. That is, a part of Ni may be substituted by Co. The containment ofCo enables a further reduction in the thermal expansion coefficient ofthe composite magnetic sealing material 2. The adding amount of Co tothe composite magnetic sealing material 2 is preferably 0.1 wt. % ormore and 8 wt. % or less.

The shape of the magnetic filler 6 is not especially limited. However,the magnetic filler 6 may preferably be formed into a spherical shapefor high packing density. Further, fillers of different particle sizesmay be blended as the magnetic filler 6 for closest packing. Further,forming the magnetic filler 6 into a spherical shape (or substantially aspherical shape) enables a reduction in damage to electronic componentsduring molding.

Particularly, for high packing density or closest packing, the shape ofthe magnetic filler 6 is preferably a true sphere. The magnetic filler 6preferably has a high tap density and a small specific surface area. Asa formation method for the magnetic filler 6, there are known a wateratomization method, a gas atomization method, and a centrifugal discatomization method. Among them, the gas atomization method is mostpreferable since it can achieve a high tap density and reduce thespecific surface area.

Although not especially limited, the surface of the magnetic filler 6 iscovered with an insulating coat 7 formed of an oxide of metal such asSi, Al, Ti, or Mg or an organic material for enhancement of flowability,adhesion, and insulation performance. To sufficiently enhance the volumeresistivity of the composite magnetic sealing material 2, the filmthickness of the insulating coat 7 is preferably set to 10 nm or more.The insulating coat 7 may be achieved by coating a thermosettingmaterial on the surface of the magnetic filler 6 or may be achieved byformation of an oxide film by hydration of metal alkoxide such astetraethyloxysilane or tetraemthyloxysilane and, most preferably, it isachieved by formation of a silicon oxide coating film. Further, morepreferably, organofunctional coupling treatment is applied to theinsulating coat 7.

The composite magnetic sealing material 2 according to the presentembodiment contains the non-magnetic filler 8. As the non-magneticfiller 8, a material having a smaller thermal expansion coefficient thanthat of the magnetic filler 6, such as SiO₂, ZrW₂O₈, (ZrO)₂P₂O₇,KZr₂(PO₄)₃, or Zr₂(WO₄)(PO₄)₂, or a material having a negative thermalexpansion coefficient is preferably used. By adding the non-magneticfiller 8 to the composite magnetic sealing material 2, it is possible tofurther reduce the thermal expansion coefficient. Further, the followingmaterials may be added to the composite magnetic sealing material 2:flame retardant such as aluminum oxide or magnesium oxide; carbon black,pigment, or dye for coloring; surface-treated nanosilica having aparticle diameter of 100 nm or less for enhancement of slidability,flowability, and dispersibility/kneadability; and a wax component forenhancement of mold releasability. It is not essential that thecomposite magnetic sealing material according to the present inventioncontains the non-magnetic filler.

Further, organofunctional coupling treatment may be applied to thesurface of the magnetic filler 6 or surface of the non-magnetic filler 8for enhancement of adhesion and flowability. The organofunctionalcoupling treatment may be performed using a known wet or dry method, orby an integral blend method. Further, the surface of the magnetic filler6 or surface of the non-magnetic filler 8 may be coated with athermosetting resin for enhancement of wettability.

When the non-magnetic filler 8 is added, the ratio of the amount of thenon-magnetic filler 8 relative to the sum of the amounts of the magneticfiller 6 and the non-magnetic filler 8 is preferably 1 vol. % or moreand 40 vol. % or less. In other words, 1 vol. % or more and 40 vol. % orless of the magnetic filler 6 can be substituted by the non-magneticfiller 8. When the additive amount of the non-magnetic filler 8 is lessthan 1 vol. %, addition effect of the non-magnetic filler 8 is hardlyobtained; on the other hand, when the additive amount of thenon-magnetic filler 8 exceeds 40 vol.%, the relative amount of themagnetic filler 6 is too small, resulting in difficulty in providingsufficient magnetic characteristics.

The composite magnetic sealing material 2 may be a liquid or solid,depending on selection of a base resin and a curing agent according tothe molding method therefor. The composite magnetic sealing material 2in a solid state may be formed into a tablet shape for transfer moldingand into a granular shape for injection molding or compression molding.The molding method using the composite magnetic sealing material 2 maybe appropriately selected from among the followings: transfer molding;compression molding; injection molding; cast molding; vacuum castmolding; vacuum printing; printing; dispensing; and a method using aslit nozzle. A molding condition may be appropriately selected fromcombinations of the base resin, curing agent and curing accelerator tobe used. Further, after-cure treatment may be applied as needed afterthe molding.

FIG. 2 is a graph illustrating the relationship between the Ni ratio ofthe magnetic filler 6 and the thermal expansion coefficient and themagnetic permeability of the composite magnetic sealing material 2. Thegraph of FIG. 2 represents a case where the magnetic filler 6 iscomposed of substantially only Fe and Ni. Here, it is assumed that theadditive amount of the magnetic filler 6 relative to the compositemagnetic sealing material 2 is 70 vol. % and no non-magnetic filler 8 isadded to the composite magnetic sealing material 2.

As illustrated in FIG. 2, when the Ni ratio of the magnetic filler 6 is32 wt. % or more and 39 wt. % or less, the thermal expansion coefficientof the composite magnetic sealing material 2 is remarkably reduced (itmay be reduced to 10 ppm/° C. in some conditions). In the example ofFIG. 2, the smallest thermal expansion coefficient (about 9.3 ppm/° C.)is obtained when the Ni ratio is about 35 wt. %. On the other hand, themagnetic permeability is not strongly correlated to the Ni ratio, and μis 12 to 13 in the range of the Ni ratio illustrated in FIG. 2.

The reason that such characteristics are obtained is that invarcharacteristics where volumetric changes due to thermal expansion andmagnetic distortion cancel out each other is exhibited when the Ni ratiofalls within the above range. A material where the invar characteristicis exhibited is called an invar material, which is known as a materialfor a die requiring high precision; however, it was not used as amaterial for the magnetic filler to be blended in a composite magneticsealing material. The present inventor pays attention to the magneticcharacteristics and small thermal expansion coefficient that the invarmaterial has and uses the invar material as a material for the magneticfiller and thereby realize the composite magnetic sealing material 2having a small thermal expansion coefficient.

FIG. 3 is a graph illustrating the relationship between the Ni ratio ofthe magnetic filler 6 and the thermal expansion coefficient of thecomposite magnetic sealing material 2. The graph of FIG. 3 represents acase where the magnetic filler 6 is composed substantially of only Feand Ni. Here, it is assumed that the additive amount of the magneticfiller 6 relative to the composite magnetic sealing material 2 is 50vol. %, 60 vol. %, or 70 vol. % and no non-magnetic filler 8 is added tothe composite magnetic sealing material 2.

As illustrated in FIG. 3, even in a case where the additive amount ofthe magnetic filler 6 is either 50 vol. %, 60 vol. %, or 70 vol. %, whenthe Ni ratio of the magnetic filler 6 is 32 wt. % or more and 39 wt. %or less, the thermal expansion coefficient of the composite magneticsealing material 2 is remarkably reduced. The more the additive amountof the magnetic filler 6 is, the smaller the thermal expansioncoefficient. Therefore, when the additive amount of the magnetic filler6 is small (e.g., 30 vol. %), the non-magnetic filler 8 formed of moltensilica is further added to reduce the thermal expansion coefficient ofthe composite magnetic sealing material 2 to 15 ppm/° C. or less.Specifically, by setting the total additive amount of the magneticfiller 6 and the non-magnetic filler 8 to 50 vol. % or more and 85 vol.% or less, the thermal expansion coefficient of the composite magneticsealing material 2 can be sufficiently reduced (e.g., to 15 ppm/° C. orless).

FIG. 4 is a graph illustrating the relationship between the Ni ratio ofthe magnetic filler 6 and the magnetic permeability of the compositemagnetic sealing material 2. As in the case of the graph of FIG. 3, thegraph of FIG. 4 represents a case where the magnetic filler 6 iscomposed substantially of only Fe and Ni and the additive amount of themagnetic filler 6 relative to the composite magnetic sealing material 2is 50 vol. %, 60 vol. %, or 70 vol. %, and no non-magnetic filler 8 isadded to the composite magnetic sealing material 2.

As illustrated in FIG. 4, even in a case where the additive amount ofthe magnetic filler 6 is either 50 vol. %, vol. %, or 70 vol. %, the Niratio and the magnetic permeability are not strongly correlated to eachother. The more the additive amount of the magnetic filler 6 is, thelarger the magnetic permeability.

FIG. 5 is a graph illustrating the relationship between the Co ratio ofthe magnetic filler 6 and the thermal expansion coefficient and magneticpermeability of the composite magnetic sealing material 2. The graph ofFIG. 5 represents a case where the sum of the amounts of Ni and Cocontained in the magnetic filler 6 is 37 wt. %, the additive amount ofthe magnetic filler 6 relative to the composite magnetic sealingmaterial 2 is 70 vol. %, and no non-magnetic filler 8 is added to thecomposite magnetic sealing material 2.

As illustrated in FIG. 5, as compared to a case where Co is notcontained (Co=0 wt. %) in the magnetic filler 6, the thermal expansioncoefficient of the composite magnetic sealing material 2 is furtherreduced when Ni constituting the magnetic filler 6 is substituted by 8wt. % or less of Co. However, when the substituted amount by Co is 10wt. %, the thermal expansion coefficient is conversely increased.Therefore, the additive amount of Co relative to the magnetic filler 6is preferably 0.1 wt. % or more and 8 wt. % or less.

FIG. 6 is a graph illustrating the relationship between the additiveratio of the non-magnetic filler 8 and the thermal expansion coefficientof the composite magnetic sealing material 2. The graph of FIG. 6represents a case where the sum of the amounts of the magnetic filler 6and the non-magnetic filler 8 is 70 vol. %, the magnetic filler 6 iscomposed of 64 wt. % of Fe and 36 wt. % of Ni, and the non-magneticfiller 8 is formed of SiO₂.

As illustrated in FIG. 6, as the ratio of the amount of the non-magneticfiller 8 is increased, the thermal expansion coefficient of thecomposite magnetic sealing material 2 is reduced; however, when theamount of the non-magnetic filler 8 exceeds 40 vol. % relative to 60vol. % of the magnetic filler 6, thermal expansion coefficient reductioneffect is nearly saturated. Thus, the amount of the non-magnetic filler8 relative to the sum of the amounts of the magnetic filler 6 andnon-magnetic filler 8 is preferably 1 vol. % or more and 40 vol. % orless.

FIG. 7 is a graph illustrating the relationship between thepresence/absence of the insulating coat 7 formed on the surface of themagnetic filler 6 and volume resistivity. Two compositions are preparedas a material for the magnetic filler 6 as follows: composition A (Fe=64wt %, Ni=36 wt. %); and composition B (Fe=63 wt. %, Ni=32 wt. %, Co=5wt. %). The insulating coat 7 is formed of SiO₂ having a thickness of 40nm. The magnetic filler 6 of either the composition A or composition Bhas a cut diameter of 32 μm and a particle diameter D50 of 20 μm.

As illustrated in FIG. 7, in both the composition A and composition B,coating with the insulating coat 7 significantly increases the volumeresistivity of the magnetic filler 6. In addition, the coating with theinsulating coat 7 reduces pressure dependency of the magnetic filler 6at the time of measurement.

FIG. 8 is a graph illustrating the relationship between the filmthickness of the insulating coat 7 formed on the surface of the magneticfiller 6 and volume resistivity. The graph of FIG. 8 represents a casewhere the magnetic filler 6 is composed of 64 wt. % of Fe and 36 wt. %of Ni. The particle diameter of the magnetic filler 6 is equal to theparticle diameter of the magnetic filler 6 in the example of FIG. 7.

As illustrated in FIG. 8, by coating the magnetic filler 6 with theinsulating coat 7 having a film thickness of 10 nm or more, the volumeresistivity of the magnetic filler 6 is increased. In particular, whenthe magnetic filler 6 is coated with the insulating coat 7 having a filmthickness of 30 nm or more, a very high volume resistivity can beobtained regardless of an applied pressure at the time of measurement.

FIG. 9 is a graph illustrating the relationship between the volumeresistivity of the magnetic filler 6 and that of the composite magneticsealing material 2.

As illustrated in FIG. 9, the volume resistivity of the magnetic filler6 and that of the composite magnetic sealing material 2 are inproportion to each other. In particular, when the volume resistivity ofthe magnetic filler 6 is 10⁵ Ωcm or more, the volume resistivity of thecomposite magnetic sealing material 2 can be increased to 10¹⁰ Ωcm ormore. When the composite magnetic sealing material 2 having a volumeresistivity of 10¹⁰ Ωcm or more is used as a molding material forelectronic circuit package, a sufficient insulating performance can beensured.

FIG. 10A is a schematic cross-sectional view illustrating a structure ofan electronic circuit package 10A using the composite magnetic sealingmaterial 2. FIG. 10B is a schematic cross-sectional view illustrating astructure of an electronic circuit package 10B using the compositemagnetic sealing material 2.

The electronic circuit package 10A illustrated in FIG. 10A includes asubstrate 20, an electronic component 30 mounted on the substrate 20,and a magnetic mold resin 40 that covers a surface 21 of the substrate20 so as to embed the electronic component 30 therein. The magnetic moldresin 40 is formed of the composite magnetic sealing material 2. Theelectronic circuit package 10B differs from the electronic circuitpackage 10A in that it further includes a metal film 60 that covers anupper surface 41 and a side surface 42 of the magnetic mold resin 40 andcovers a side surface 27 of the substrate 20. In both the electroniccircuit packages 10A and 10B, the substrate 20 has a thickness of 0.25mm, and the magnetic mold resin 40 has a thickness of 0.50 mm.

FIG. 11 is a graph illustrating noise attenuation in the electroniccircuit package 10B. The metal film 60 is composed of a laminated filmof Cu and Ni, and two types of metal films 60 whose Cu films havedifferent thicknesses are evaluated. Specifically, the metal film 60 ofsample A has a configuration in which the Cu film having a thickness of4 μm and the Ni film having a thickness of 2 μm are laminated, and themetal film 60 of sample B has a configuration in which the Cu filmhaving a thickness of 7 μm and the Ni film having a thickness of 2 μmare laminated. For comparison, values of samples C and D each formed byusing a molding material not containing the magnetic filler 6 are alsoshown. The metal film 60 of sample C has a configuration in which the Cufilm having a thickness of 4 μm and the Ni film having a thickness of 2μm are laminated, and the metal film 60 of sample D has a configurationin which the Cu film having a thickness of 7 μm and the Ni film having athickness of 2 μm are laminated.

As illustrated in FIG. 11, when the composite magnetic sealing material2 containing the magnetic filler 6 is used, noise attenuation effect isenhanced especially at a frequency band of 100 MHz or less as comparedto a case where the molding material not containing the magnetic filler6 is used. Further, it can be seen that the larger the thickness of themetal film 60, the higher the noise attenuation performance.

FIGS. 12 to 14 are graphs each illustrating the relationship between thefilm thickness of the metal film 60 included in the electronic circuitpackage 10B and noise attenuation. FIG. 12, FIG. 13, and FIG. 14illustrate the noise attenuation in the frequency bands of 20 MHz, 50MHz, and 100 MHz, respectively. For comparison, a value obtained when amolding material not containing the magnetic filler 6 is also shown.

As illustrated, in all the frequency bands of FIGS. 12 to 14, the largerthe thickness of the metal film 60, the higher the noise attenuationperformance. Further, by using the composite magnetic sealing material 2containing the magnetic filler 6, it is possible to obtain higher noiseattenuation performance in all the frequency bands of FIGS. 12 to 14,than in a case where a molding material not containing the magneticfiller 6.

FIG. 15 is a graph illustrating the warp amount of the substrate 20during temperature rising and that during temperature dropping in theelectronic circuit packages 10A and 10B. For comparison, values obtainedwhen the magnetic filler 6 is substituted by the non-magnetic fillerformed of SiO₂ are shown in FIG. 16.

As illustrated in FIG. 15, the warp amount of the substrate 20 causeddue to a temperature change is smaller in the electronic circuit package10B having the metal film 60 than in the electronic circuit package 10Anot having the metal film 60. Further, as is clear from a comparisonbetween FIGS. 15 and 16, the warp characteristics of the respectiveelectronic circuit packages 10A and 10B using the composite magneticsealing material 2 containing the magnetic filler 6 are substantiallyequivalent to the warp characteristics of the respective electroniccircuit packages 10A and 10B using a molding material containing thenon-magnetic filler formed of SiO₂.

While the preferred embodiments of the present invention have beendescribed, the present invention is not limited thereto. Thus, variousmodifications may be made without departing from the gist of theinvention, and all of the modifications thereof are included in thescope of the present invention.

Examples <Production of Composite Magnetic Sealing Material>

A resin material was prepared with 830S (bisphenol A epoxy resin) madeby Dainippon Ink & Chemicals, Inc., used as a base resin, with 0.5equivalent of DicyDD (Digi Angi amide) made by Nippon Carbide IndustriesCo., Inc. added to the base resin as a curing agent, and with 1 wt. % ofC11Z—CN (imidazole) made by Shikoku Chemicals Corporation added to thebase resin as a curing accelerator.

50 vol. %, 60 vol. %, or 70 vol. % of a magnetic filler having thecomposition illustrated in FIG. 17 was added to the above resinmaterial, followed by intensive kneading to obtain a paste. If pastingfailed, butylcarbitol acetate was added appropriately. The obtainedpaste was coated to a thickness of about 300 μm and then heat-curedsequentially at 100° C. for one hour, at 130° C. for one hour, at 150°C. for one hour, and at 180° C. for one hour in this order, to obtain acured sheet. The composition 1 (comparative example) is a magneticmaterial generally called PB Permalloy.

<Measurement of Thermal Expansion Coefficient>

The above cured sheet was cut to a length of 12 mm and a width of 5 mm.Then, TMA was used to raise temperature from room temperature to 200° C.at 5° C./min, and a thermal expansion coefficient was calculated fromthe amount of expansion in a temperature range of 50° C. to 100° C.which is lower than a glass transition temperature. The measurementresults are shown in FIG. 18. In FIG. 18, the measurement resultobtained when the non-magnetic filler formed of SiO₂ is used in place ofthe magnetic filler is also shown.

As illustrated in FIG. 18, when the magnetic filler having thecomposition 2 or 3 is used, the thermal expansion coefficient issignificantly reduced as compared to when the magnetic filler having thecomposition 1 (comparative example) is used. In particular, when theadditive amount is 60 vol. % or more, a thermal expansion coefficientequivalent to that obtained when the non-magnetic filler formed of SiO₂is used is obtained, and when the additive amount is 70 vol. %, thethermal expansion coefficient is as small as 10 ppm/° C. or less.

<Measurement of Magnetic Permeability>

The above cured sheet was cut into a ring shape having an outer diameterof 7.9 mm and an inner diameter of 3.1 mm. Then, the material analyzerfunction of impedance analyzer E4991 manufactured by Agilent Corp., Ltd.was used to measure an effective magnetic permeability (μ′) at 10 MHz.The measurement results are shown in FIG. 19.

As illustrated in FIG. 19, the magnetic permeability obtained when themagnetic filler having the composition 2 or 3 is substantiallyequivalent to the magnetic permeability obtained when the magneticfiller having the composition 1 (Comparative Example) is used.

<Considerations>

The composite magnetic sealing material obtained by adding the magneticfiller having the composition 2 or 3 to a resin material has a thermalexpansion coefficient equivalent to the thermal expansion coefficientobtained when the non-magnetic filler formed of SiO₂ is used and has amagnetic permeability equivalent to the magnetic permeability obtainedwhen the magnetic filler formed of PB permalloy is used. Thus, by using,as a sealing material for an electronic circuit package, the compositemagnetic sealing material obtained by adding the magnetic filler havingthe composition 2 or 3 to a resin material, it is possible to obtainexcellent magnetic shielding characteristics while preventing the warpof the substrate, interfacial delamination or crack of a moldingmaterial.

1. A composite magnetic sealing material comprising: a resin material;and a filler blended in the resin material in a blended ratio of 30 vol.% or more to 85 vol. % or less, wherein the filler includes a magneticfiller containing Fe and 32 wt. % or more and 39 wt. % or less of ametal material composed mainly of Ni, thereby a thermal expansioncoefficient of the composite magnetic sealing material is 15 ppm/° C. orless.
 2. The composite magnetic sealing material as claimed in claim 1,wherein the metal material further contains 0.1 wt. % or more and 8 wt.% or less of Co relative to a total weight of the magnetic filler. 3.The composite magnetic sealing material as claimed in claim 1, whereinthe filler further includes a non-magnetic filler.
 4. The compositemagnetic sealing material as claimed in claim 3, wherein a ratio of anamount of the non-magnetic filler relative to a sum of an amounts of themagnetic filler and the non-magnetic filler is 1 vol. % or more and 40vol. % or less.
 5. The composite magnetic sealing material as claimed inclaim 4, wherein the non-magnetic filler contains at least one materialselected from a group consisting of SiO2, ZrW2O8, (ZrO)2P2O7,KZr2(PO4)3, or Zr2(WO4)(PO4)2.
 6. The composite magnetic sealingmaterial as claimed in claim 1, wherein the magnetic filler has asubstantially spherical shape.
 7. The composite magnetic sealingmaterial as claimed in claim 1, wherein the magnetic filler is coatedwith an insulating material.
 8. The composite magnetic sealing materialas claimed in claim 7, wherein a film thickness of the insulatingmaterial is 10 nm or more.
 9. The composite magnetic sealing material asclaimed in claim 1, wherein the resin material comprises a thermosettingresin material.
 10. The composite magnetic sealing material as claimedin claim 9, wherein the thermosetting resin material contains at leastone material selected from a group consisting of an epoxy resin, aphenol resin, a urethane resin, a silicone resin, or an imide resin. 11.The composite magnetic sealing material as claimed in claim 1, wherein avolume resistivity of the composite magnetic sealing material is 1010 Wcm or more.
 12. A composite magnetic sealing material comprising: aresin material; a magnetic filler formed of an Fe—Ni based materialblended in the resin material, the magnetic filler containing Fe and 32wt. % or more and 39 wt. % or less of a metal material composed mainlyof Ni; and a non-magnetic filler blended in the resin material, whereina ratio of an amount of the non-magnetic filler relative to a sum of anamounts of the magnetic filler and the non-magnetic filler is 1 vol. %or more and 40 vol. % or less, and wherein a thermal expansioncoefficient of the composite magnetic sealing material is 15 ppm/° C. orless.
 13. (canceled)
 14. The composite magnetic sealing material asclaimed in claim 12, wherein the magnetic filler is coated with aninsulating material having a film thickness is 10 nm or more.
 15. Thecomposite magnetic sealing material as claimed in claim 12, wherein thenon-magnetic filler contains at least one material selected from a groupconsisting of SiO2, ZrW2O8, (ZrO)2P2O7, KZr2(PO4)3, or Zr2(WO4)(PO4)2.16-19. (canceled)